PEXppSx 0Ak Sx

qEn x,=variable

In [10], E\pP and EXit are the exergy destructions of the entire process and of the kth component respectively, linked to the efficiency by

Einput

If the ith thermodynamic variable Xj is varied, the result is a change in the efficiencies of some of the components: the sensitivity of each component is measured by dExt/dx. At a higher aggregation level, the coefficient of structural bonds aki measures the sensitivity of the process to a variation of the efficiency of the kth component'. But the variation of the efficiency of components that operate on quantitatively small exergy flows is not as important for the process as that of a major component that elaborates the main' fluxes of exergy: this aspect is quantified by the influence coefficient k, If a variation of the ;th thermodynamic variable Xj causes a variation in the magnitude of a certain exergy flux E, Kj measures the influence of this variation on the overall input of the process.

Once <j and k are known, we can analyze formally, that is, without recurring to a numerical process simulation, the influence on the output of a variation in the inputs of the process. The problem is, of course, that to obtain these coefficients we must recur either to an extensive experimental campaign or to numerical process simulations.

Components

Fluxes

1

2

3

4

5

6

7

8

9

10

11

12

13

C

1

-1

0

0

0

1

0

0

0

0

0

0

0

CC

0

1

1

-1

0

0

0

0

0

0

0

0

0

T

0

0

0

1

-1

-1

-1

0

0

0

0

0

0

A

0

0

0

0

0

0

1

-1

0

0

0

0

0

HRB

0

0

0

0

1

0

0

0

-1

0

1

-1

0

P

0

0

0

0

0

0

0

0

0

1

-1

0

1

Figure 7 The connectivity matrix CM associated with the cogeneration plant of Figure 3.

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